The Little Man Computer RAM Random Access Memory

The Little Man Computer

ﺍﻧﻮﺍﻉ ﺣﺎﻓﻈﻪ ﺍﺻﻠی RAM( Random Access Memory) ROM( Read Only Memory) PROM( Programmable ROM) EPROM( Erasable PROM)

ROM ¨ Non-volatile memory to hold software that is not expected to change over the life of the system ¨ Magnetic core memory ¨ EEPROM – Electrically Erasable Programmable ROM – Slower and less flexible than Flash ROM ¨ Flash ROM – Faster than disks but more expensive – Uses • BIOS: initial boot instructions and diagnostics • Digital cameras

ﻇﺮﻓیﺖ ﺣﺎﻓﻈﻪ ﻇﺮﻓیﺖ ﻣﺤﺎﺳﺒﻪ ﺑﺮﺍی ﻓﺎکﺘﻮﺭ ﺩﻭ ¨ MAR ﻫﺎی ﺑیﺖ ﺗﻌﺪﺍﺩ -1 LMC = 100 (00 to 99) • 2 K where K = width of the register in bits • ﺩﺳﺘﻮﺭﺍﻟﻌﻤﻞ آﺪﺭﺱ ﻗﺴﻤﺖ -2 4 bits allows 16 locations • 8 bits allows 256 locations • 32 bits allows 4, 294, 967, 296 or 4 GB • کﺎﺭﺍیی ﺩﺭ ﺣﺎﻓﻈﻪ ¨ ﺍﻫﻤیﺖ Insufficient memory can cause a processor to work at 50% – below performance

Cache

Fetch-Execute Cycle Two-cycle process because both instructions ¨ and data are in memory Fetch ¨ Decode or find instruction, load from memory into – register and signal ALU Execute ¨ Performs operation that instruction requires – Move/transform data –

MDR ﻭ MAR ﺭﺍﺑﻄﻪ ﺑیﻦ Address Data

MAR-MDR msb(memory storage buffer) lsb(latest significant byte) ﻣﺜﺎﻝ

Load Fetch/Execute Cycle 1. PC -> MAR Transfer the address from the PC to the MAR 2. MDR -> IR Transfer the instruction to the IR 3. IR(address) -> MAR Address portion of the instruction loaded in MAR 4. MDR -> A Actual data copied into the accumulator 5. PC + 1 -> PC Program Counter incremented

Store Fetch/Execute Cycle 1. PC -> MAR 2. MDR -> IR 3. IR(address) -> MAR Transfer the address from the PC to the MAR Transfer the instruction to the IR Address portion of the instruction loaded in MAR 4. A -> MDR* Accumulator copies data into MDR 5. PC + 1 -> PC Program Counter incremented *Notice how Step #4 differs for LOAD and STORE

ADD Fetch/Execute Cycle 1. PC -> MAR Transfer the address from the PC to the MAR 2. MDR -> IR Transfer the instruction to the IR 3. IR(address) -> MAR Address portion of the instruction loaded in MAR 4. A + MDR -> A Contents of MDR added to contents of accumulator 5. PC + 1 -> PC Program Counter incremented

Instruction Elements ¨ OPCODE: task ¨ Source OPERAND(s) Addresses ¨ Result OPERAND – Location of data (register, memory) • Explicit: included in instruction • Implicit: default assumed OPCODE Source OPERAND Result OPERAND

Instruction Types ¨ Data Transfer (load, store) – Most common, greatest flexibility – Involve memory and registers – What’s a word ? 16? 32? 64 bits? ¨ Arithmetic – Operators + - / * ^ – Integers and floating point ¨ Logical or Boolean – Relational operators: > < = – Boolean operators AND, OR, XOR, NOR, and NOT ¨ Single operand manipulation instructions – Negating, decrementing, incrementing

More Instruction Types ¨ Bit manipulation instructions – Flags to test for conditions ¨ Shift and rotate ¨ Program control ¨ Stack instructions ¨ Multiple data instructions ¨ I/O and machine control ﺩﻛﺘﺮ ﻛﺎﻫﺎﻧﻲ - ﻣﺒﺎﻧی کﺎﻣپیﻮﺗﺮ

Register Shifts and Rotates

Stack Instructions ¨ Stack instructions – LIFO method for organizing information – Items removed in the reverse order from that in which they are added Push Pop

Fixed Location Subroutine Return Address Storage:

Point-to-point vs. Multipoint Plug-in device Broadcast bus Example: Ethernet Shared among multiple devices

PC ﺍﺭﺗﺒﺎﻃﺎﺕ ﺩﺭ AGP(Accelerated Graphics Port) PCI(Peripheral Component Interconnect) ISA(Industry Standard Architecture)

Basic Model ¨ Processing speed or program execution – determined primarily by ability of I/O operations to stay ahead of processor. Input Process Output

I/O Considerations Speed Issues ¨ CPU operates at speeds much faster than the fastest I/O device ¨ Devices operate at different speeds ¨ Character device, there is not any addressing or searching, printer, network card… ¨ Block devices (disk or tape drive) Coordination ¨ Several devices perform I/O simultaneously ¨ Unexpected input ¨ Various input formats ¨ Status information needed for each device

I/O Device Interface Issues ¨ Different formats – parallel interface – serial interface ¨ Buffering of data ¨ Burst vs. stream ¨ Different control requirements – electromechanical

Examples of I/O Devices

Simple I/O Configuration

I/O Modules Functions ¨ Recognizes messages from device(s) addressed to it and accepts commands from the CPU ¨ Provides a buffer where the data from memory can be held until it can be transferred to the disk ¨ Provides the necessary registers and controls to perform a direct memory transfer ¨ Physically controls the device ¨ Copies data from its buffer to the device/from the CPU to its buffer ¨ Notifies with interrupts

Input/Output Modules ¨ Programmed I/O – CPU controlled I/O ¨ Interrupt Driven I/O – External input controls ¨ Direct Memory Access Controllers – Method for transferring data between main memory and a device that bypasses the CPU

Programmed I/O

Programmed I/O Example

Programmed I/O Example

Interrupts ¨ Signal that causes the CPU to alter its normal flow on instruction execution – frees CPU from waiting for events – provides control for external input ¨ Examples – unexpected input – abnormal situation – illegal instructions – multitasking, multiprocessing

The CPU - The Interrupt Cycle § Fetch / Execute cycle § Interrupt cycle START Fetch Next Instruction HALT Execute Instruction Interrupts Disabled Check/Process Interrupt

Interrupt Terminology ¨ Interrupt lines (hardware) ¨ Interrupt request ¨ Interrupt handlers – Program that services the interrupt – Also known as an interrupt routine ¨ Process Control Block (PCB) – Located in a part of memory known as the stack area – All registers of a program are saved here before control is transferred to the interrupt handler

Interrupt Terminology ¨ Servicing the interrupt – suspends program in progress – saves pertinent information including last instruction executed and data values in registers in the PCB (process control block) – branches to interrupt handler

Servicing an Interrupt

Use of Interrupts ¨ Notify that an external event has occurred – real-time or time-sensitive ¨ Signal completion – printer ready or buffer full ¨ Allocate CPU time – time sharing ¨ Indicate abnormal event (CPU originates for notification and recovery) – illegal operation, hardware error ¨ Software interrupts

Multiple Interrupts Example

Basic CPU-Memory-I/O Pathway

External Interface Buses and Ports ¨ Parallel port ¨ Serial port – RS-232 C and RS-422 buses ¨ SCSI – Small Computer System Interface ¨ USB, USB-2 – Universal Serial Bus

Storage Devices ¨ Primary memory ¨ Expanded storage ¨ Secondary storage – Data and programs must be copied to primary memory for CPU access – Permanence of data – Direct access storage devices (DASDs) – Online storage – Offline storage – loaded when needed

Speed ¨ Measured by access time and data transfer rate ¨ Access time: average time it takes a computer to locate data and read it – millisecond = one-thousandth of a second ¨ Data transfer rate: amount of data that moves per second

Hierarchy of Storage

Secondary Storage Devices ¨ Hard drives, floppy drives ¨ CD-ROM and DVD-ROM drives ¨ CD-R, CD-RW, DVD-RAM, DVD-RW ¨ Tape drives ¨ Network drives ¨ Direct access vs. Sequential access ¨ Rotation vs. Linear

Magnetic Disks ¨ ¨ ¨ Track – circle Cylinder – same track on all platters Block – small arc of a track Sector – pie-shaped part of a platter Head – reads data off the disk ¨ ¨ Head crash Parked heads Number of bits on each track is the same! Denser towards the center. CAV – constant angular velocity – Spins the same speed for every track – Hard drives – 3600 rpm – 7200 rpm – Floppy drives – 360 rpm

A Hard Disk Layout

Locating a Block of Data ¨ Average seek time: time required to move from one track to another ¨ Latency: time required for disk to rotate to beginning of correct sector ¨ Transfer time: time required to transfer a block of data to the disk controller buffer

Disk Access Times ¨ Avg. Seek time – average time to move from one track to another ¨ Avg. Latency time – average time to rotate to the beginning of the sector – Avg. Latency time = ½ * 1/rotational speed ¨ Transfer time – 1/(# of sectors * rotational speed) ¨ Total Time to access a disk block – Avg. seek time + avg. latency time + avg. transfer time

Magnetic Disks ¨ Data Block Format Disk Interleaving – Interblock gap – Header – Data – Formatting disk ¨ Disk Interleaving ¨ Disk Arrays – RAID – mirrored, striped – Majority logic fault-tolerant computers

Disk Block Formats Single Data Block Header for Windows disk

Alternate Disk Technologies ¨ Removable hard drives – Disk pack – disk platters are stored in a plastic case that is removable – Another version includes the disk head and arm assembly in the case ¨ Fixed-head disk drives – One head per track – Eliminates the seek time ¨ Bernoulli Disk Drives – Hybrid approach that incorporates both floppy and hard disk technology – Zip drives

Optical Storage ¨ Reflected light off a mirrored or pitted surface ¨ CD-ROM – Spiral 3 miles long, containing 15 billion bits! – CLV – all blocks are same physical length – Block – 2352 bytes • 2 k of data (2048 bytes) • 16 bytes for header (12 start, 4 id) • 288 bytes for advanced error control ¨ DVD-ROM – 4. 7 G per layer – Max 2 layers per side, 2 sides = 17 G

Optical Storage ¨ Laser strikes land: light reflected into detector ¨ Laser strikes a pit: light scattered

Layout: CD-ROM vs. Standard Disk CD-ROM Hard Disk

CD-ROMs

Types of Optical Storage ¨ WORM Disks – Write-once-read-many times – Medium can be altered by using a medium-powered laser to blister the surface – Data stored in concentric tracks, sectored like a magnetic disk ¨ Medium-powered laser blister technology also used for – CD-R, DVD-ROM – CD-RW, DVD-RAM, DVD+RAM

Displays ¨ Pixel – picture element ¨ Size: diagonal length of screen ¨ Resolution (pixels on screen) – VGA: 480 x 640 – SVGA: 600 x 800 – 768 x 1024 – 1280 x 1024 ¨ Picture size calculation – Resolution * bits required to represent number of colors in picture – Example: 16 color image, 100 pixels by 50 pixels 4 bits (16 colors) * 100 * 50 = 20, 000 bits

Display Screen ¨ Screen size: measured diagonally ¨ Resolution: minimum identifiable pixel size ¨

Color and Displays ¨ Pixel color is determined by intensity of 3 colors – Red Green Blue or RGB ¨ 4 bits per color – 16 x 16 = 4096 colors ¨ 24 bit color (True Color) – 16. 7 million colors ¨ Video memory requirements are significant!

Text Monitors – 24 lines x 80 chars – A character is the smallest unit on a screen – Very little memory required – Fast for remote transmissions

Printers ¨ Dots vs. pixels – 300 -2400 dpi vs. 70 -100 pixels per inch – Dots are on or off, pixels have intensities ¨ Types – Typewriter /– obsolete – Dot matrix – usually 24 pins, impact printing – Inkjet – squirts heated droplets of ink – Laser jet

Creating a Gray Scale

Laser Printer Operation 1. 2. 3. 4. 5. 6. 7. Dots of laser light are beamed onto a drum Drum becomes electrically charged Drum passes through toner which then sticks to the electrically charged places Electrically charged paper is fed toward the drum Toner is transferred from the drum to the paper The fusing system heats and melts the toner onto the paper A corona wire resets the electrical charge on the drum

Laser Printer Operation

Laser Printer Operation

Other Computer Peripherals ¨ Scanners – Flatbed, sheet-fed, hand-held – Light is reflected off the sheet of paper ¨ User Input Devices – Keyboard, mouse, light pens, graphics tablets ¨ Communication Devices – Telephone modems – Network devices

ﻧﻤﻮﻧﻪ ﻇﺮﻓﻴﺖ ﻭﺳﻴﻠﻪ ﻧﻮﻉ 20 -300 g Hard Disk 1. 4 m Floppy Disk 700 m CD 5. 2 g DVD 250 m Zip 4 - 100 g Tape

System Software Programs that maintain operation of computer Two types are operating systems and utility programs Operating system (OS) (sometimes called the platform) coordinates all activities among computer hardware resources p. 398

Operating System ¨ A program that controls the execution of application programs ¨ An interface between applications and hardware

Operating System ¨ Management – Memory – Process – i/o – file ¨ Virtual machine

Layers of Computer System

Services Provided by the Operating System ¨ Program development – Editors and debuggers ¨ Program execution ¨ Access to I/O devices ¨ Protected access to files

Services Provided by the Operating System ¨ Error detection and response – internal and external hardware errors • memory error • device failure – software errors • arithmetic overflow • access forbidden memory locations – error recovery

Uniprogramming ¨ Processor must wait for I/O instruction to complete before preceding

Multiprogramming When one job needs to wait for I/O, the ¨ processor can switch to the other job

Multiprogramming

Time Sharing ¨ Using multiprogramming to handle multiple interactive jobs ¨ Processor’s time is shared among multiple users ¨ Multiple users simultaneously access the system through terminals

Main OS Concepts ¨ Processes ¨ Memory Management ¨ Information protection and security ¨ Scheduling and resource management ¨ System structure

Processes ¨ A program in execution ¨ An instance of a program running on a computer ¨ The entity that can be assigned to and executed on a processor ¨ A unit of activity characterized by a single sequential thread of execution, a current state, and an associated set of system resources

Process ¨ Consists of three components – An executable program – Associated data needed by the program – Execution context of the program • All information the operating system needs to manage the process

Process

Memory Management ¨ Process isolation ¨ Automatic allocation and management ¨ Support for modular programming ¨ Protection and access control ¨ Long-term storage

Virtual Memory ¨ Allows programmers to address memory from a logical point of view

File System ¨ Implements long-term store ¨ Information stored in named objects called files

Paging ¨ Allows process to be comprised of a number of fixed-size blocks, called pages ¨ Virtual address is a page number and an offset within the page ¨ Each page may be located any where in main memory ¨ Real address or physical address in main memory

Virtual Memory Addressing

Types of Operating Systems Stand-alone: complete operating system working on PC, laptop, mobile computing device. like DOS, Windows, Mac OS X, Unix, Linux Network: OS designed specially to support a network, like netware, windows server 2003, Unix, Linux and Solaris Embedded : OS on most PDA and small devices Like, windows CE, windows mobile 2003, Palm OS and Symbian OS

Stand-Alone Operating Systems DOS (Disk Operating System) • Developed in early 1980 s for personal computers • Hardly used today because it does not offer GUI • Used command-line interface when first developed, later included menus

Stand-Alone Operating Systems Microsoft Windows Version Year Released Windows 3. x 1990 Windows NT 3. 1 1993 Windows 95 1995 Windows NT Workstation 4. 0 1996 Windows 98 1998 Windows Millennium Edition 2000 Windows 2000 Professional 2000 Windows XP 2001

Stand-Alone Operating Systems Mac OS X Ø Available only for computers manufactured by Apple Ø Macintosh operating system has been model for most GUIs

Stand-Alone Operating Systems OS/2 Warp Client Ø Ø IBM’s GUI multitasking operating system Supports networking, Java, the Internet, and speech recognition

Stand-Alone Operating Systems UNIX Ø Used by power users because of its flexibility and power Ø Most versions offer GUI Ø Both a stand-alone and a network operating system

Stand-Alone Operating Systems Linux Ø Popular, free, multitasking UNIX-type operating system Ø Open-source software code is available to public Ø Both a stand-alone and a network operating system e Red Hat provides a version of Linux called Red Hat Linux. The GNOME graphical user interface is shown in this example.

Network Operating Systems ¨ Allows users to share printer, Internet access, ¨files, and programs on a network ¨ Administers security by establishing ¨user name and password for each user Solaris Net. Ware Designed for client/server networks Windows Server 2003 § Version of UNIX developed by Sun Microsystems Upgrade to Windows 2000 Server § Specifically for e-commerce applications OS/2 Warp Server for e-business IBM’s network operating system for businesses

Embedded Operating Systems Ø Found on most mobile computers, PDAs, and other small devices Ø Windows CE is scaled-down version of Windows

Embedded Operating Systems operating systems for PDAs ¨ Ø Ø Ø Pocket PC 2002 for Pocket PC Ø Newer versioins: Windows Mobile 5 & 6 Palm OS for Palm, Visor, and CLIE Embeded Linux

Embedded Operating Systems Mobile Operating systems • Windows Mobile Smartphone • A scaled down version of PDAs • Symbian Ø Ø Open-source, multitasking operating system designed for smart phones Make telephone calls, save appointments, browse Web, send and receive e-mail and faxes, and more

Utility Programs ¨ disk scanner Ø Ø Detects and corrects problems on hard disk or floppy disk Searches for and removes unnecessary files § backup utility Ø Ø Copies selected files or entire hard disk onto another disk or tape compress files during backup to require less storage space

Utility Programs disk defragmenter ¨ Ø Reorganizes files and unused space on hard disk so programs run faster fragmented disk file before defragmenting file after defragmenting

Utility Programs ¨ screen saver Ø Causes monitor’s screen to display moving image or blank screen if there is no activity for a specified time Ø To secure computer, user configures screen saver to require password to deactivate

Utility Programs ¨ diagnostic utility Ø Compiles technical information about hardware and some software Ø Prepares report outlining problems

Stand-Alone Utility Programs ¨ What is a virus? Ø Ø Potentially damaging computer program Affects computer without user’s knowledge SIGNS OF VIRUS INFECTION

Stand-Alone Utility Programs ¨ antivirus program Ø Ø Identifies and removes viruses in memory, storage media, and incoming files Must be updated frequently

Stand-Alone Utility Programs ¨ file compression utility Ø Shrinks size of files to free up room and improve performance Ø Compressed files are sometimes called zipped files, or rared files Ø Two popular utilities: Win. RAR and Win. Zip®

Stand-Alone Utility Programs ¨ personal firewall Ø Protects personal computer from unauthorized intrusions Ø Monitors all transmissions to and from computer